The ability to transfer a color proof composite to any media provides a convenient means for one to view a simulated color print prior to investing in the expense and labor of printing a job on a printing press. It also provides an inexpensive means for constructing mock-up samples where only a few samples are needed. This is particularly useful in designing imaged package materials. For example, several mock-up samples with slight variations can be constructed for comparative studies to evaluate general marketing impact and appeal. Many approaches have been disclosed in the art using different methods in combination with different imaging technologies.
For example, image transfer systems using conventional color proofing materials based on colored photoresists are described in U.S. Pat. Nos. 3,721,557; 4,376,158; 4,376,159; 4,482,625; 4,766,053; 5,094,931; and 5,192,630. In a colored photoresist system, an image is formed by exposing a photosensitive layer to actinic radiation and then developed with a liquid developer. The developing solution may be solvent based or aqueous based depending upon the formulation of the photoresist. The developer is used to wash away the non-imaged areas and then disposed of either immediately or after reuse to exhaustion by discharging into a drain or sending to a waste disposal site.
U.S. Pat. No. 2,528,395 describes an image transfer system where a diazo-type photosensitive coating is applied to a substrate having a pressure-sensitive adhesive attached to the backside of the substrate. The material is exposed and developed with ammonia fumes. The imaged film is then transferred to any substrate via the pressure-sensitive adhesive. Other transfer systems using pressure sensitive adhesive are also known e.g., U.S. Pat. Nos. 3,987,225 and 4,111,734. The use of pressure sensitive adhesives has several disadvantages such as lack of dimensional stability, the image is easily scratched or torn, and the surface of the composite is easily disrupted by objects lying on the surface.
Image transfer systems using liquid and dry electrophotographic and electrostatic generated images are also known. Representative examples of these types of transfer system may be found in U.S. Pat. Nos. 4,383,878; 4,686,163;
More recently, transfer systems and materials using dye, mass transfer, and ablative transfer films in laser or thermal head printers have grown in popularity. Examples of these types of transfer systems may be found in U.S. Pat. Nos. 4,902,669; 4,923,848; 5,055,444; 5,077,263; 5,372,987; and 5,633,116. In each of these systems, the non-imaged portions of the donor element retain non-transferred material which makes it difficult to recycle the spent carrier film.
None of the aforementioned image transfer systems provide ideal systems with regard to environmental disposal or efficient use of materials. Some of the systems require liquid developers which are either discharged directly into a drain or sent to a waste disposal site. The Electrophographic systems use liquid toners based on organic solvents which raise concerns for emissions of volatile organic compounds thus requiring means for recovering the solvent and disposal. Dry toner systems use toner powders which become air borne and inhaled. The diazo-type materials require the use of ammonia fumes which have a repugnant smell and are difficult to contain. Therefore, there is a need for an image transfer system that minimizes disposal of unused materials, reduces emissions of volatile organic compounds and provides recyclable spent materials.